Know your stuff. Part 2: Glass

Glass is one of the most beautiful and useful materials out there. From cups to windows, vases to plates, to more complex uses, glass plays an essential role for industry and science. 

The Aalto vase dates back to 1936 and was first presented at the Paris World Fair the following year.

Before people learned to make glass, they had found two forms of natural glass. When lightning strikes sand, the heat sometimes fuses the sand into long, slender glass tubes called fulgurites, which are commonly called petrified lightning. The terrific heat of a volcanic eruption also sometimes fuses rocks and sand into a glass called obsidian. In early times, people shaped obsidian into knives, arrowheads, jewelry, and money. It is generally believed that the first manufactured glass was in the form of a glaze on ceramic vessels, about 3000 B.C. The first glass vessels were produced about 1500 B.C. in Egypt and Mesopotamia. The glass industry was extremely successful for the next 300 years, and then declined. It was revived in Mesopotamia in the 700's B.C. and in Egypt in the 500's B.C. For the next 500 years, Egypt, Syria, and the other countries along the eastern shore of the Mediterranean Sea were glassmaking centers.

Early glassmaking was slow and costly, and it required hard work. Glass blowing and glass pressing were unknown, furnaces were small, the clay pots were of poor quality, and the heat was hardly sufficient for melting. But glassmakers eventually learned how to make colored glass jewelry, cosmetics cases, and tiny jugs and jars. People who could afford them—the priests and the ruling classes—considered glass objects as valuable as jewels. Soon merchants learned that wines, honey, and oils could be carried and preserved far better in glass than in wood or clay containers.

:Blown glass. The blowpipe was invented around 30 B.C. This invention made glass production easier, faster, and more accessible. As a result, glass became available to the common people for the first time. 

 

Glass manufacture became important in all countries under Roman rule. The glassmakers of this time knew how to make a transparent glass, and they did offhand glass blowing, painting, and gilding (application of gold leaf). They knew how to build up layers of glass of different colors and then cut out designs in high relief. The celebrated Portland vase, discovered near Rome around 1625, is an excellent example of this art. This vase is considered one of the most valuable glass art objects in the world.

The Barberini vase or Portland Vase as it became known as, is the most famous cameo-glass vessel from antiquity. it has  been studied for centuries by scholars trying to determine its original utilitarian purpose and the perplexing meaning of its idyllic scenes.

:Color. You may wonder how glass can become such vibrant colors. Early glass derived its color from impurities that were present when the glass was formed. For example, 'black bottle glass' was a dark brown or green glass, first produced in 17th Century England. This glass was dark due to the effects of the iron impurities in the sand used to make the glass and the sulfur from the smoke of the burning coal used to melt the glass.

In addition to natural impurities, glass is colored by purposely introducing minerals or purified metal salts (pigments). Examples of popular colored glasses include ruby glass (invented in 1679, using gold chloride) and uranium glass (invented in the 1830s, glass that glows in the dark, made using uranium oxide).

Colourful Maribowls have been in production since the 1960s.

The ruby red color is one of the most expensive glasses because it is colored with gold chloride. Gold(III) chloride is most often prepared by passing chlorine gas over gold powder at 180 °C:    

2 Au + 3 Cl₂ → 2 AuCl₃

Another method of preparation is the reaction in which solid gold is placed in a solution of aqua regia to give chloroauric acid. Heating liberates hydrogen chloride, giving gold(III) chloride:
    Au₂Cl₆ + 2 HCl → 2 HAuCl₄

Here is a list of natural impurities that are added to make glass pigmented.

Compounds	Colors
iron oxides	greens, browns
manganese oxides	deep amber, amethyst, decolorizer
cobalt oxide	deep blue
gold chloride	ruby red
selenium compounds	reds
carbon oxides	amber/brown
mix of mangnese, cobalt, iron	black
antimony oxides	white
uranium oxides	yellow green (glows!)
sulfur compounds	amber/brown
copper compounds	light blue, red
tin compounds	white
lead with antimony	yellow

Other examples of beautiful glass uses from Iittala of Finland:

Ultima Thule by Tapio Wirkkala: Inspired by the melting ice in Lapland, Wirkkala originally created the surface in the 1960s after carving into a graphic mould. An exclusive design reflecting the thousands of hours spent perfecting the glass-blowing technique required to produce the effect. The patterns gradually change as the glass burns the surface of the wooden moulds.

Kastehelmi by Oiva Toika: The Finnish name ‘dewdrop’ refers to the circles of bubbles in the pressed glass. Inspired by Finnish nature, the dewdrops glisten like a string of pearls on grass in the morning sun. Oiva Toikka’s love for experimentation led to the creation of an entirely new droplet design for Kastehelmi.

Aino Aalto by Aino Aalto: Echoing rings of water, this pressed glassware from 1932 is tactile proof that essential design survives the test of time. Simple, space saving design that permits stacking and versatility were the starting point for these classics. In production since its launch, Aino Aalto glassware now celebrates 80 years of design history and today continues to drive the Iittala design thinking forward.

References

http://en.wikipedia.org/wiki/Glass

http://www.texasglass.com/glass_facts/history_of_Glass.htm

http://madamepickwickartblog.com/2010/03/as-the-world-urns/

http://chemistry.about.com/cs/inorganic/a/aa032503a.htm 

http://en.wikipedia.org/wiki/Gold%28III%29_chloride

http://www.iittala.com